TT Ari and two sure winners

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Wed, 16 Nov 2005 05:30:09 -0500 (EST) · jop_at_astro.columbia.edu

Dear Tom and CBAers,

TT Ari is often a very good target this time of year - being so bright,
tantalizing us with a sheaf of periods, and more or less accessible to
both hemispheres.  Tom has obtained a few consecutive nights at very high
time resolution, and Bill Allen and Jennie McCormick have also covered it
from NZ.

There was an early report of the star's fading, a rare event of much
interest in this type of star ("VY Scl star").  But then it popped back up
again to ~10.6... does it deserve to stay on our menu?  Well, I looked at
this year's coverage.  Same old TT Ari, seducing with that annoying 20
minute QPO... and largely (or perhaps altogether) missing any trace of
superhump.  We know that novalikes turn off their superhump machines
episodically, so this is not of substantial interest by itself.  In some
future golden age, we - or someone - may actually get enough data to show
how the superhump machine turns on/off... but at present this is far
beyond us.  The 20 minute signal may yield to tenacious observers a bit
earlier; I think it will, but I also think we're not quite ready to wage
that big a war on it.  So my response to Tom's question is:

(1) As far as we know, time resolution beyond 30-60 s is not needed on TT
    Ari;
(2) the star should be mostly dropped from our menu (mainly for failing to
    yield a superhump signal); and
(3) it remains of interest for very bright-moon conditions, when some of
    our hotshot targets have trouble surviving the background light.

The two stars I want to commend with maximal enthusiasm right now are BW
Scl and HS2331+39 (one of the "And" stars in the Downes et al the
catalog).  Each is ~16.5, with very strong signals at 35.5 cycles/day -
basically twice the orbital frequency.  And each has a raft of other
periods it flashes at us.  These are poster-child stars for period
finding: the raw light curves (in smallscope data) are so ugly and the
period-search results are so beautiful!  And they're sittin' up there in
the evening sky symmetrically placed for N and S observers... these stars
are just one CBA observing season away from the cataclysmic-variable Hall
of Fame!

And a little later in the night for N observers, FS Aur rolls back into
view.  As some of you know, this star continues to baffle with its
inscrutable 3.5 hr photometric signal of unknown origin.  Let's grab it
early in the season and not let it go till it vanishes in those March
sunsets!

BTW we have now established that we will have a CBA meeting coincident
with the SocAstroSoc (formerly IAPPP) meeting in Big Bear, CA during May
24-26, 2006.  Since they'll have 100+ people and we'll have maybe 10-12,
we'll just be a small part of their meeting - so you should just register
for their meeting.  In the next 2-3 weeks, some more information will be
coming re this.

joe